The next person who says "I can't wait until the Army develops real mecha" gets a boot to the head, because in real life, mecha are actually really stupid. Here's why:
Bipedal robots are stupid

Pretty much since the dawn of robotics, we've been trying to find a way to make robots walk on two legs. Not because anybody needs robots to walk on two legs, but just to prove it can be done. And while it is possible now, with millions of dollars of technology and advanced software, it still can't be done well. Try and get Asimo to walk up stairs or, you know, move quickly and you get the picture. Bipedal locomotion is hard. That's why it's rare in nature.

Compare the number of two-legged creatures to those sporting four, six, or eight legs and you'll realize that bipedal is a gross minority position, for a variety of reasons. Four legs is a minimal base for stability—just ask any table. You could get by with three legs, but you you abandon bilateral symmetry, which virtually every creature on Earth has, and you also give up some basic redundancy. A four-legged creature can get by on three legs in a pinch, but a biped isn't going far hopping on one foot. Also, being bipedal means that any rest state requires a change in position—you can't sleep standing up. Thus, if a bipedal mecha were to lose power—or just be turned off—it would at best be left in a vulnerable state that was easy to push over, and at worst would collapse into a heap of mangled, unconscious robot wreckage. Sure, mecha are as tall as skyscrapers, but they don't have that handy bolted-to-the-ground thing to keep them from toppling in a swift wind. (Even with quadrupeds, stability can be an issue if you don't set up a low center of gravity. Case in point: AT-ATs.)

Biologically, most bipeds started out as quadrupeds and gave up the forelegs (and four legs) to convert them into some more specialized appendage — say, a wing or a grasping, tool-using hand. When you can flat-out design a function-specific battlebot, you don't need to make these kinds of zero-sum tradeoffs. Which brings up another point...

Robot hands are stupid

The whole point of a hand is to grasp tools and objects. That's what it's for. Now, if you're a giant robot, what exactly are you grasping, apart from the giant energy sword that exists solely to justify the creation of your giant hands? Again, when you're custom-building a combat robot, you don't have to make a generic interface like a hand, you can just weld the energy blades, rocket launchers, laser cannons and whatnot right onto the frakkin' robot where they can't be dropped.

Sure, you can pick up some cars and hurl them for sport, but that's hardly an efficient use of resources. And there are better climbing implements than human-style fingers and thumbs — setting aside the fact that there's almost nothing out there with the structural integrity to handle the weight of a mecha trying to climb it. Also, a lion's mouth for a hand is cool looking but hideously impractical. Then again, so are flying robot lions.

Giant robots are stupid

What, exactly, is the point of being the size of the Chrysler Building, unless your job is to fight the Chrysler Building? (Please don't, the American auto industry has enough problems.) If Godzilla shows up, I might spot you the on-a-lark tactic of meeting the radioactive reptile with an equal-scale automated countermeasure, especially if conventional weaponry has failed and King Kong is busy filming a sequel with Peter Jackson. But since reality is tragically short on kaiju city-wreckers, what's the point?

Most mecha are depicted as military weapons, but not even armed navies like to build things any bigger than they have to. Aircraft carriers are a quarter-mile long because it's a necessary length to land and launch planes. Everything else about their scale flows from that design constraint. Most every classic naval battleship has been retired because speed, agility, and coordinated attack — the kind that GPS, computerized communications, and precision-targeted ordnance make possible — are prized over bulk tonnage. We'd rather have a swarm of destroyers and fast-attack boats than one big dreadnought, if only to avoid the issue of making a big giant target. Same goes for robot warriors.

Basically, giant humanoid military mechas are stupid

All of the above sets aside the fact that (at least according to Wired) it would cost $725 million just to build a basic mecha from existing tech, and that doesn't even include any of the cool super weapons — or, for that matter, the actual development, design, and systems integration costs needed to build a super robot from off-the-shelf parts.

This is not to say that uber-bots will never exist, just that they won't look anything like a Gundam.

In a general sense, legs are better than wheels or even treads when it comes to dealing with uneven terrain and extreme grades. Legs don't need flat surfaces with minimal obstacles, so a quadrupedal (or better) robot is actually an advantage in many situations. Like, say, other planets that haven't seen much civilization. Thus, we're likely to see walking robots in the future — on four or more legs. (For all the film's remaining idiocy, the AMEE droid from Red Planet is actually a pretty clever and workable take on what an explorer robot would look like.)

We may also see large-scale robots in the future as the technology becomes available to automate — and make autonomous — large industrial equipment. Robot cranes, trucks, excavators and loggers are very likely on the horizon. Just make sure they're programmed not to squish the environmental protesters they encounter (unless the protesters start building androids to replace their numbers, too).

Humanoid robots also have a role to play — in places where they will operate in shared environments with humans. Every building on Earth is designed by and for humans, so rather than redesign every edifice on the planet to accommodate our new cybernetic overlords, simply make the robots human-like, so they can walk up stairs, open doors and operate human-friendly equipment with us.

What is unlikely is a confluence of gigantic, humanoid, ambulatory, military robots — better known as mecha. Anyone who says otherwise needs to detox from the anime and take an engineering course or two.

About Jay Garmon

Jay Garmon has a vast and terrifying knowledge of all things obscure, obtuse, and irrelevant. One day, he hopes to write science fiction, but for now he'll settle for something stranger — amusing and abusing IT pros. Read his full profile. You can a...

Full Bio

Jay Garmon has a vast and terrifying knowledge of all things obscure, obtuse, and irrelevant. One day, he hopes to write science fiction, but for now he'll settle for something stranger — amusing and abusing IT pros. Read his full profile. You can also follow him on his personal blog.